Tensioning apparatus for extrusion presses



July 7, 1959 E. D. DAVIES 2,893,552

TENSIONING APPARATUS FOR EXTRUSION PRESSES Filed Oct; 27, 1955 4Sheets-Sheet 1 1\ I INVENTOR Y ENOCH D. DAVIES ATTORNEY July 7, 1959 E.D. DAVIES TENSIONING APPARATUS FOR EXTRUSION PRESSES Filed 001;. 27,1955 4 Sheets-Sheet 2 iNVENTOR ENOCH D. DAVIES WWW ATTORNEY July 7, 1959E. D. DAVIES 2,893,552

TENSIONING APPARATUS FOR EXTRUSION PRESSES Fil ed Oct. 27. 1955 4Sheets-Sheet 3 lNVENTOR ENOOH D. DAVIES ATTORNEY- July 7, 1959 E. D.DAVIES 2,893,552

' mnslomuc APPARATUS FOR EXTRUSION PRESSES Filed 001;. 27, 1955 4Sheets-Sheet 4 FIG. 8

d 1 h? --G.| 22 I ENVENTOR ENOGH D. DAVIES ATTORNEY United States PatentTENSIONING APPARATUS FOR EXTRUSION PRESSES Enoch D. Davies, Wild Rose,Wis., assignor to The Oilgear Company, Milwaukee, Wis., a corporation ofWisconsin Application October 27, 1955, Serial No. 543,103

Claims. (Cl. 207-4) This invention relates to apparatus for maintainingten-- sion on material as it is being extruded through a die.

Apparatus embodying the invention is particularly adapted to maintaintension on extrusions of aluminum during the extruding operation and theinvention will be explained as being employed for that purpose, but itis not limited to that particular use.

An aluminum extrusion press ordinarily includes a container to receivethe material to be extruded, a die which is rigidly held in contact withthe front end of the container during the extruding operation and hasone or more holes of the desired configuration extending therethrough, aram to enter the rear end of the container and force material therefromthrough the holes in the die, and a hydraulic motor for operating theram. If the cross-sectional area of the extrusion is relatively large,the die may have only one or two holes extending therethrough but, ifthe cross-sectional area of the extrusion is small, the die may beprovided with a larger number of holes, such as five holes.

Extrusion is effected by placing a billet of aluminum in the containerand starting the motor which will advance the ram into the container andcause it to force aluminum from the billet through the die. Theextrusions thus formed pass onto a table, the top of which is coatedwith a graphited composition to prevent it from marring the extrusions.

The motor is at first operated at a slow speed to cause the extrusionsto emerge slowly from the die until the end of each extrusion has beengrasped by an attendant with vise-grip pliers and then the motor isspeeded up to cause the material to be extruded at a predeterminedmaximum rate, such as three feet per second. At the present time, theattendants walk along the table, which in some cases is sixty feet long,and each attendant guides his extrusion along the table to keep it fromengaging and being marred by any other extrusion. Thus there must be asmany attendants as there are holes in the die, particularly as thecharacteristics of the holes in the die cause the extrusions to emergeat difierent rates. Also, each attendant should pull on his extrusionwith suflicient force to keep it reasonably straight.

When the extrusions reach the desired length or when the billet isnearly consumed, the ram is retracted and the motor stopped. Then theextrusions are sheared from the remaining portion of the billet, thusleaving the ends of the extrusions in the die from which they must bestripped ice die and will strip them from the die at the end of theextruding operation.

Other objects and advantages will appear from the following descriptionof the embodiments of the invention shown schematically in theaccompanying drawings in which the views are as follows:

Fig. 1 is a hydraulic circuit diagram of a tensioning apparatus in whichthe invention is embodied.

Fig. 2 is a section taken on the line 2--2 of Fig. 1 but drawn to alarger scale and with the reduction gear casings and the hydraulicmotors shown in full.

Fig. 3 is a top plan view of parts of the tensioning apparatus with thetop plate removed, the plane of the view being indicated by the line 3-3of Fig. 2.

Fig. 4 is a transverse section taken on the line 4--4 of Fig. 3.

, Fig. 5 is a longitudinal section taken on the line 5-5 of Fig. 3.

Fig. 6 is a view drawn to a larger scale than Fig. 5 and showing avise-grip plier which is used for gripping an extrusion and has a hookfor engaging a chain such as that shown in Fig. 5.

Fig. 7 is a sectional plan view of certain parts and a plan view ofother parts of a tensioning apparatus for use with a machine which makesfive extrusions at a time, the sections being taken approximately on theirregular line 7--7 of Fig. 8.

Fig. 8 is a transverse section taken on the line 8-8 of Fig. 7.

Fig. 9 is a view showing how a tensioning apparatus may be arrangedabove the extrusion die instead of below it as is the case with thetensioning apparatus shown in the other views.

An embodiment of the invention has been shown in Fig. 1 as beingassociated with an extrusion press having a stationary container 1 toreceive an aluminum billet 2, a die 3 which is rigidly held against theouter end of container 1 during an extruding operation and has two holes4 extending therethrough, a hydraulically operated ram 5 and a buttshear 6. The other parts of the press have not been illustrated becausethe press per se forms no part of the present invention. It is deemedsufficient to state herein that ram 5 is advanced by a hydraulic motor(not shown) and forces metal from billet 2 through holes 4 to form anextrusion 7 having the same cross-sectional configuration as holes 4 andthat, at the end of the extruding operation, die 3 is moved away fromcontainer 1 and shear 6 is advanced and shears extrusion 7 from theremainder of billet 2. Each hole 4 is tapered and increases incross-sectional area from its entrance end toward its exit end but Fig.l is drawn to such a small scale that the taper cannot be shown.

FIGS. 1-6

The tensioning apparatus shown in these figures includes an elongatedtable comprising a frame 8 and a top plate 9 having two slots 10 and 10extending there through for the greater part of its length. The table isarranged parallel to the axis of ram 2 with the end of plate 9 adjacentto die 3 and somewhat below holes 4.

Frame 8 has two drive shafts 11 and 11 journaled in its opposite sidesnear its left end and two sprocket wheels 12 and 12 are fixed on shafts11 and 11 in alignment with slots 10 and 10 respectively. Shaft 11 isconnected to a hydraulic motor M1 through a reduction gear G1 and shaft11 is connected to a motor M1 through a reduction gear G1.

Sprockets 12 and 12 are connected, respectively, by two roller linkchains 15 and 15 to two idler sprocket wheels 16 and 16 which arearranged in alignment with slots 10 and 10, respectively, and journaledon a shaft 17 carried by frame 8 near the right end thereof.

The inlets of the motors M1 and M1 are connected by a channel '18 to theoutlet of a pump P1 which has its inlet connected to a reservoir 19 by achannel 20 having a check valve 21 arranged therein. Pump P1 when drivenwill draw liquid from reservoir 19 and discharge it into channel 18. Theoutlets of motors M1 and M1 are connected to an exhaust channel 22 whichdischarges into the reservoir 19. When the motors are energized byliquid from pump P1, they will rotate shafts 11 and 11 and cause theupper reaches of chains 15 and 15 to travel away from die 3, and theliquid discharged by the motors will flow through channel 22 intoreservoir 19.

The parallel connection of the hydraulic motors provided by channel 18is a hydraulic means that causes the hydraulic motors to share the flowof fluid from the pump inversely in accordance with their hydraulicresistances. This results in the rate of flow to each motor beingproportionate to their torque rating and the proportionate flow to eachmotor varying inversely with changes in its torque load relative to thetorque load on the other motor. Where the tensions should be equal,therefore, the flow rate through each motor and therefore the speedresponds to the lineal speed of its attached extrusion in order tomaintain the same tension thereon as on each of the other extrusions.

In order to prevent an unloaded motor from racing when another motor isloaded, a flow control valve is connected in series with each motor. Theflow control valves may control the rates at which liquid enters themotors or the rates at which liquid is discharged therefrom. Asshown, afiow control valve V1 is connected into a branch of exhaust channel 22in series with'motor M1- and a flow control valve V1 is connected into abranch of exhaust channel 22 -in series with motor M1. The two flowcontrol valves are alike and each comprises an orifice choke 23 and apressure regulating valve 24 which maintains a constant pressure'at theinlet of choke 23.

In order that pump P1 may continue to run when motors M1 and Ml areidle, means are provided for bypassing the pump. As shown, a bypassvalve 25 is con nected between channels 18 and 22. Valve 25 comprises avalve body 26 having an axial bore 27 and two annular grooves or ports28 and 29 formed in the wall of the bore, a valve member 30 which isfitted in the bore and controls communication between the ports, and aspring 31 which normally holds valve member 30 in open position asshown. Port 28 is connected to channel 18 by a channel 32 and port 29 isconnected to channel 22 by a channel 33. Valve 25 may be closed in anysuitable manner such as by a solenoid 34 connected to thestem of thevalve member 30.

The arrangement is such that, when pump P1 is running and valve 25 isopen as shown, all of the liquid discharged by pump P1 will flow throughchannels 18 and 32, valve 25 and channels 33 and 22 into reservoir 19.Then when solenoid 34 is energized, it will raise valve member 30 whichwill block port 28 and thereby cause the liquid discharged by pump P1 toflow through channel 18 to motors M1 and M1 to energize the same.

Pump P1 may be of any type which has a member shiftable to vary itsdisplacement and a control which will cause the pump to discharge liquidat predetermined maximum rate until pump pressure reaches a predeter--mined maximum and will then reduce pump displacement until the pump isdelivering just enough liquid to maintain that pressure constant.

For the purpose of illustration, the pump has been indicated as being ofthe rolling piston type disclosed in Patent No. 2,074,068, and as havinga pressure responsive control of the type disclosed in Patent No.2,080,810. Since both the pump and the pump control are well "known andin extensive commercial use, it is deemed su'fiicient to state hereinthat pump P1 includes a displacement varying member or slide block 38which is arranged in a casing 39 andis shiftable therein between aneutral or zero displacement position and a maximum displacementposition, and that pump P1 when driven will discharge liquid intochannel 18 at a rate proportional to the distance slide block 38 isoffset from its neutral position.

Slide block 38 is urged toward maximum displacement position by aconstant force which may be provided by a spring or, as shown, by aservo-motor comprising a cylinder 40 which is carried by casing 39 and apiston 41 which is fitted in cylinder 40 and engages or is fixed to aslide block 38. Liquid for energizing servo-motor 4041 is suppliedby agear pump P2 which when driven will draw liquid from reservoir 19 anddischarge it into a branched channel 42, one branch of which isconnected to cylinder 40. Liquid discharged by pump P2 in excess ofrequirements is exhausted through a low pressure relief valve 43 whichenables pump P2 to maintain a constant low pressure in channel 42 andcylinder 40. For the purpose of illustration, pump P2 has been shownseparate from pump P1 but in practice it is driven in unison with pumpP1 and arranged within the casing thereof as is customary.

Slide block 38 is adapted to be moved toward zero displacement positionby a hydraulic servo-motor shown as comprising a cylinder 44, which iscarried by casing 39, and a piston 45 which is fitted in cylinder 44 andengages or is fixed to slide block 38. Movement of slide block 38 towardmaximum displacement position is limited by a suitable stop shown asbeing an adjusting screw 46 which is threaded through the head ofcylinder 44 and is normally engaged by piston 45. Adjustment of screw 46determines the maximum displacement of pump -P1.

Liquid for operating servo-motor 44-45 is supplied thereto underthecontrol of a control valve 50 having its mechanism arranged within acasing 51. In practice, valve 50 is quite small and casing 51 isattached directly to pump casing 39 but for the purpose of illustrationvalve 50 has been shown separated from casing 39 and on a greatlyenlarged scale Casing '51 has formed therein an axial bore 52 which isconnected to the discharge side of pump P1 by a channel 53, an annulargroove or port 54 which is formed in the wall of bore 52 and isconnected to cylinder 44 by a channel 55 having a choke 56 arrangedthereinto limit the rate at which liquid can flow into cylinder 44, anda counterbore 57 which is larger than and concentric with bore 52 and isclosed at its upper end by a cover plate 58.

Flow of liquid into and out of cylinder 44 is controlled by a valvemember consisting of a valve element 59, which is closely fitted in bore52 and has at least one notch 60 formed in its lower end, and a piston61 which is fixed to element 59 and is closely fitted in counterbore 57.Any pressure created by pump P1 will extend through channel 53 into bore52 and tend to move valve member 59-61 toward the left against theresistance of a spring 62 arranged between piston 61 and a piston 63which is closely fitted in counterbore 57 and provides between its upperface and the lower face of cover plate 58 a pressure chamber 64 to whichthe liquid under pressure is supplied as will presently be explained.

The force exerted by spring 62 is initially regulated by an adjustingscrew 65 which is threaded through cover plate 58 and engages piston 63until the force exerted by the liquid in chamber 64 exceeds the forcewith which spring -62urges piston 63 against screw 65 and then piston 63will further compress spring 62 and the pressure required to raise valvemember 59-61 will be proportional to thepressure in chamber 64.

In order that liquid may escape from cylinder 44 when the control valveis closed, the space between pistons 76 1 and 63 ,isflconnected to adrain and piston 61 is urn a provided in its upper edge with a pluralityof small tapered grooves or slots 66 which communicate when the valve isclosed with an annular groove or port 67 which is formed in the wall ofcounterbore 57 and is connected to cylinder 44 by a channel 68. p

. The parts preferably are so constructed that the vertical distancebetween slots 60 and 66 is exactly equal to the vertical distancebetween the lower edge of port 54 and the upper edge of port 67. Whenthe pressure created by pump P1 has reached a predetermined value asdetermined by the resistance of spring 62 or by the pressure in chamber64, it will have moved valve member 5961 towardthe left until the bottomof slot 60 is even with the lower edge of port 54 and the bottoms ofslots 66 are even with the upper edge of port 67 so that there isno flowof liquid either into or out of cylinder 44. 1

Then a slight increase in pump pressure will cause valve member 59-61 tomove farther toward the left and permit liquid to flow from channel 53through bore 52, slot 60, port 54 and channel 55 into cylinder 44 andcause piston 45 to shift slide block 38 toward the right to reduce pumpdisplacement until pump P1 is discharging just enough liquid to maintainpump pressure at a predetermined value. Conversely, a slight drop inpump pressure permits spring 62 or the pressure in chamber 64 to movevalve member 59-61 toward theright to partly uncover port 67 so thatliquid can escape from cylinder 44 through channel 68, port 67 andcounterbore 57 to drain, thereby permitting servo-motor 4041 to moveslide block 38 toward the left to increase pump displacement until pumpP1 is discharging enough liquid to maintain pump pressure at thepredetermined value.

Liquid is supplied to pressure chamber 64 from pump P2 under the controlof a valve 72 comprising a valve body 73 having an axial bore 74 and twoannular grooves or ports 75 and 76 formed in the wall of the bore, avalve member 77 fitted in bore 74 and a spring 78 which urges valvemember 77 to a position in which chamber 64 is connected to drain.Chamber 64 is connected by a channel 79 to bore 74 at a point betweenport 75, which has a branch of channel 42 connected thereto, and port 76which communicates with an exhaust channel 80 which discharges intoreservoir 19.

With valve member 77 in the position shown, it would appear from thedrawing that all of the liquid in chamber 64 and channel 79 could escapeinto reservoir 19 but, preferably, means are provided to prevent theliquid from escaping such as by arranging valve 72 at least as high asvalve 50 or by inserting a low pressure resistance valve in channel 80.

When valve member 77 is shifted toward the left, liquid from channel 42will flow through valve 72 and channel 79 into chamber 64 and will causepiston 63 to move toward the right and compress spring 62, therebyenabling pump P1 to create a pressure proportional to the resistance ofrelief valve 43. Valve member 77 may be shifted toward the left in anysuitable manner such as by means of a solenoid 81 which is connected tothe stem of valve member 77.

Operation Before an extruding cycle is started, pump P1 is running andis discharging liquid through channels 18 and 32, valve and channels 33and 22 into reservoir 19 at a maximum rate as determined by theadjustment of screw 46. Then closing valve 25 will divert the liquidthrough channel 18v to motors M1 and M1 and cause them to rotate shafts11 and 11 and sprocket wheels 12 and 12 The liquid discharged by motorsM1 and M1 will flow through valves V1 and V1 and channel 22 to reservoir19.

' Pump P1 will at first attempt to deliver liquid to the motors at amaximum rate but valves V1 and V1 limit the rate at which liquid canflow therethrough, thereby causing pump pressure to rise and liquid toilow from block 38 toward the right and thereby reduce the displacementof pump P1 until it is delivering just enough liquid to maintainconstant the pressure determined by the adjustment of screw 65. I

As the pump displacement decreases, spring 62 will move valve element 59toward the right and, when the pump is delivering just enough liquid tomaintain the predetermined pressure constant, the left end of notch 60will be in alignment with the edge of port 54 and the bottoms of theslots 60 in piston 61 will be in alignment with the left hand edge ofport 67 so that liquid is trapped in cylinder 44 and holds slide block38 stationary.

The rotation of sprocket wheels 12 and 12 causes chains 15 and 15 totravel therearound and around sprocket wheels 16 and 16 respectively,and the upper reaches of the chains to travel away from die 3. Thespeeds of motors M1 and M1 are determined by the adjustment of valves V1and V1 which are so adjusted that the linear speeds of chains 15 and 15are slightly greater than the maximum speeds at which extrusions 7emerge from die 3.

The extrusion press at first causes extrusions 7 to emerge at a slowspeed. After each extrusion has emerged a short distance, an attendantgrasps the end of it with a vise-grip plier 4 (Fig. 6) having a hook 85pivotally connected thereto and he then inserts the hook through one ofthe slots 10 or 10 in top plate 9 and into engagement with the chain 15or 15* underneath that slot as indicated in Fig. 6. Hook 85 is slideablefreely in the slot and it is wide enough to keep the plier substantiallyparallel to the slot. As soon as hook 85 engages the chain, the motordriving that chain is slowed down because valve 50 is so adjusted thatthe pressure created by pump P1 is just sufficient to enable the motorto maintain a predetermined tension upon the extrusion, such as a pullof 30 pounds. Slowing down the motor results in pump P1 tending todeliver more liquid than is required to drive the motors but valve 50will function in the above described manner to reduce pump displacementuntil the liquid discharged by pump P1 is just sufficient to drive themotors.

When all of the extrusions have been connected to the chains, the pressis speeded up and the metal isextruded through die 3 at a maximum rate.Increasing the extruding rate causes a momentary drop in pump pressurewhich enables spring 62 to move valve element 59--61 toward the rightand liquid to escape from cylinder 44, thereby enabling servo-motor40-41 to move slide block 38 toward the left to increase the deliveryrate of pump P1 and piston 45 to eject liquid from cylinder 44 throughchannel 68, port 67, slot 66 and counterbore 57 to exhaust. As soon aspump P1 is delivering enough liquid to maintain the predeterminedpressure constant, valve 50 will operate in the above described mannerto stop further movement of slide block 38.

When the extrusions reach the desired lengths or when billet 2 is nearlyexhausted, the press is stopped which causes extrusions 7 to stopemerging from die 3. Then die 3 is moved a short distance away fromcontainer 1 and stopped and immediately thereafter shear 6 is advancedand cuts extrusions 7 from the remainder of billet 2. Stopping theextrusions causes the motors to stall and pump pressure to rise, movingdie 3 away from container 1 causes pump pressure to drop and stoppingdie 3 causes the motors to stall and pump pressure to rise but controlvalve 50 responds to the change in pressure and efiects in the abovedescribed manner the necessary variations in the displacement of pump P1to enable it to maintain the pressure substantially constant and therebyenable the motors to maintain constant tension upon the extrusions.

After extrusions 7 have been sheared from the remainder of billet 2,valve 72 is shifted to connect pressure chamber 64 in valve 50 topressure channel 42. .Then the pressure created by pump P2 will act uponpisa, greater pressure than is necessary to enable the motor to stripthe extrusions from the die.

FIGS. 7 AND 8 The tensioning apparatus shown in these figures differsfrom the apparatus shown in Figs. 1-6 only in that it is adapted tomaintain tension on five extrusions at the same time. Therefore,corresponding parts have been indicated by corresponding referencenumerals but with different exponents added to the reference numeralsapplied to Figs. 7 and 8.

' As shown, the apparatus includes an elongated table comprising astationary frame 8 and a top plate 9 which is fixed to the top of frame8' and has five slots 10 10,- 10 10 and 10 extending therethrough forthe greater part of its length. Frame 8 has five shafts 11 11, 11 li and11 journaled therein near its left end and connected through reductiongears G1 G1 G1 G1", and G1 to hydraulic motors Ml- M1, Ml Ml and Mlrespectively. In order that an attendant may approach close to plate 9when removing extrusions of maximum length from the table, motor M1 maybe arranged inside of frame 8 as shown.

Shafts 11 and 11 have two sprocket wheels 12 and 12 fixed thereondirectly beneath slots 10* and 10, respectively. Shafts 11 11 and I1have three sprocket wheels 12 12 and 12 fixed thereon directly beneathslots 10 10 and 10, respectively. Sprocket wheels 12 12", 12 12*, and Elare connected by five endless chains 15 15, 15 15*, and 15 respectively,to five idler sprocket wheels 16 16, 16 16, and 16 which are journaledupon a shaft 7 carried by frame 8 near the right end thereof.

Each of motors M1 M1 Ml M1 and M1 has a branch of pressure channel 18(Fig. 1) and a branch of exhaust channel 22 connected thereto, and aflow control valve similar to valve VI (Fig. 1) is connected in serieswith each motor. The tensioning apparatus shown in Figs. 7 and 8functions in exactly the same manner as the apparatus shown in Figs. 1-6but it is capable of maintaining equal tension upon five extrusionssimultaneously as they emerge from a die, and it is also capable ofstripping the extrusions from the die at the end of the extrudingoperation as previously explained.

FIG. 9

This figure illustrates how the sprocket and chains of a tensioningapparatus, such as that shown in Figs. 7 and 8, may be arranged above anextrusion press which has been represented by a container 1 to receivethe material to be extruded, a die 3 a ram and a shear 6 The press hasan elongated table 89 arranged in front of and below die 3 as iscustomary.

The tensioning apparatus includes a frame 8 which is connected at itsright end to the frame of the press (not shown) by a support 90 and itis connected at its left endto table 89 by a support 91. Frame 8 hasattached to its lower face a plate 9 having as many elongated slots (notshown) therein as there are holes in die 3 and it carries as many chainsand the drives therefor as there are holes in die 3 with the lower reachof each chain directly above one of the slots in plate 9;

- For the purpose of illustration, the mechanism carried 8 by plate 9has been indicated as being the same as that which is carried by frame 8but is reversed in respect thereto. Therefore, such parts as appear in-Fig. 9 have been indicated by the same reference numerals as thecorresponding parts shown in the mechanism shown in Fig. 7 so thatfurther description thereof is unnecessary.

The tensioning apparatus operates in the previously described manner butafter a plier 84 (Fig. 6) has been clamped on an extrusion, the hook 85is inserted through a slot in plate 9 and engaged with the lower reachof the chain in alignment with that slot. Arranging the pullingmechanism above the die is of particular advantage when a maximum numberof extrusions having very small cross-sectional areas are extrudedsimultaneously be cause, when the pulling mechanism is arranged belowthe die and there are slots in the top plate of the table, there isdanger that some extrusions might be marred by coming in contact withthe corners formed on the plate by the slots since it is impossible tokeep the corners coated with the composition, but with the pullingmechanism arranged above the die there are slots in the top of the table89 and, therefore,- there is no danger of the small extrusions beingmarred by the corners formed by the slots.

The tensioning apparatus described herein may be modified in variousways without departing from the scope of the invention which is herebyclaimed as follows:

1. In combination with an extrusion press including a die having aplurality of holes through which a billet of material is pushed to'emerge in a plurality of extrusions at lineal rates that tend todiiferfrom one another, tensioning means comprising ahydraulic pump,- aplurality of hydraulic motors, means connecting said hydraulic motorshydraulically in parallel with each other and with said pump, valvemeans connected in series with each of said hydraulic motors to limitthe maximum rate of fluid flow therethrough for limiting the maximumspeeds of said hydraulic motors to a value greater than the corresp'ondingrate said extrusions emerge from said die, a plurality ofdriven members each operatively connected to a shaft of a different oneof said hydraulic motors, and means attaching said driven members todiiie'rent said extrusions so that said apparatus applies and maintainsan equal pull on each of said extrusions.=

2. Apparatus for use with an extrusion press having a die with aplurality of holes through which a mass of material is' pushed to emergein a plurality of extrusions at lineal rates' that may differ from oneanother, said apparatus comprising a variable delivery hydraulic pumpincluding regulating means for maintaining pump discharge at apredetermined pressure; a plurality of hydraulic motors connectedhydraulically in parallel with each other and in common to said pump,now control valves each connected in series with a different said motorto limit the maximum speed thereof fo a predetermined value, individualpairs of driven and idler sprockets each engaged by a continuous chain,and separate detachable means adapted for independent attachment to eachsaid chain and to each said extrusion for separate movement therewith sothat said apparatus maintains each said extrusion at a tension equal tothe tension on each other said extrusion.

3. In combination with an extrusion press including a die having aplurality of holes through which a billet of material is forced underpressure to emerge from a front face of the die in a plurality ofextrusions corresponding to said holes and at lineal rates that are notuniform, a variable delivery hydraulic pump selectively operable atrelatively low and high output pressures, a plurality of hydraulicm'otors connected in parallel with each other and with said pump, valvemeans connected in series with each said hydraulic motor to limit therate of fluid flow therethr'oug'h, a plurality of mechanical deviceseach coupled independently to difie'rent said hydraulic motors andincluding clamping members each adapted for attachment to acorresponding one of said extrusions; whereby, when said pump operatesat said low output pressure said motors maintain each of said extrusionsat equal tension insufl'icient to pull the material through said die; ashear device for shearing remaining said billet material from the backface of said die at the end of a press cycle for said extrusion press,and manually operable control means causing said pump to operate at saidhigh pressure after said shearing has taken place so that said hydraulicmotors strip said extrusions from the die.

4. Apparatus for use with an extrusion press having a die with aplurality of holes through which a mass of material is pushed andemerges from a front face of the die in a plurality of extrusions atlineal rates that may difier from one another, said apparatus comprisinga variable delivery hydraulic ptnnp, a plurality of hydraulic motorsconnected hydraulically in parallel with said pump, valve meansconnected in series with each said hydraulic motor to limit the rate offlow of fluid therethrough for limiting the speed of said motors to apredetermined value, a movable means operatively connected to each saidhydraulic motor for movement thereby in a direction away from said dieat a speed tending to exceed the speed of movement of said extrusions,means attaching each said movable means to different said extrusions,said hydraulic pump having a displacement varying member shiftable tovary the stroke of said pump, means continuously urging saiddisplacement member in a direction to increase pump stroke, a servomotor operative to urge said displacement member in an oppositedirection to decrease pump stroke, a control valve operativelyconnecting said servo motor to the outlet of said pump to limit thestroke of said pump and maintain said pump pressure at a firstpredetermined value sufiicient to cause said hydraulic motors tomaintain each of said extrusions at equal tension that is not sufficientto pull said extrusions from said die, a solenoid valve hydraulicallyconnected to said control valve and operative to supply fluid underpressure thereto in opposition to the outlet pres- 4 sure of said pumpto increase the stroke of said pump for raising the outlet pressure ofsaid pump above said predetermined value to thereby give said hydraulicmotors suflicient torque to pull said extrusions from said die; whereby,said apparatus is selectively operable to tension said extrusions asthey are formed and to pull said extrusions from the die in a strippingoperation at the end of an extrusion cycle.

5. Apparatus for use with an extrusion press in which a mass of materialis pushed through a pair of holes in a die and forms a pair ofextrusions that emerge from the die at different lineal rates, means formaintaining a predetermined tension on each of said extrusions, saidtensioning means comprising a variable delivery hydraulic pump, a pairof hydraulic motors, means connecting said hydraulic motors in parallelwith each other and in common with said pumps, a first continuous chainand sprocket means coupled to one of said motors, a second continuouschain and sprocket means coupled to a second one of said motors, a firstdetachable means connecting said first chain to one of said extrusionsfor movement therewith away from said die, a second detachable meansconnecting said second chain to the other of said extrusions formovement therewith away from said die, and means regulating said pump tosupply fluid to said motors at a predetermined pressure sufficient forapplying said predetermined tension to said extrusions and notsuflicient for pulling said extrusions through or from said die.

References Cited in the file of this patent UNITED STATES PATENTS644,919 Illingworth Mar. 6, 1900 2,056,896 Douglas Oct. 6, 19362,074,068 Ferris Mar. 16, 1937 2,080,810 Douglas May 18, 1937 2,332,069Gettig Oct. 19, 1943 2,720,310 Yack et a1 Oct. 11, 1955 FOREIGN PATENTS159,973 Australia Nov. 25, 1954 284,085 Great Britain Jan. 26, 1928192,471 Germany Dec. 2, 1907

